Protection of Modern Power Systems

Familiarize yourself with the cutting edge of power system protection technology

All electrical systems are vulnerable to faults, whether produced by damaged equipment or the cumulative breakdown of insulation. Protection from these faults is therefore an essential part of electrical engineering, and the various forms of protection that have developed constitute a central component of any course of study related to power systems. Particularly in recent decades, however, the demands of decarbonization and reduced dependency on fossil fuels have driven innovation in the field of power systems. With new systems and paradigms come new kinds of faults and new protection needs, which promise to place power systems protection once again at the forefront of research and development.

Protection of Modern Power Systems offers the first classroom-ready textbook to fully incorporate developments in renewable energy and ‘smart’ power systems into its overview of the field. It begins with a comprehensive guide to the principles of power system protection, before surveying the systems and equipment used in modern protection schemes, and finally discussing new and emerging protection paradigms. It promises to become the standard text in power system protection classrooms.

Protection of Modern Power Systems readers will also find:

• Treatment of the new faults and protection paradigms produced by the introduction of new renewable generators
• Discussion of SmartGrids—intelligently-controlled active systems designed to integrate renewable energy into the power system—and their protection needs
• Detailed exploration of Synchronized Measurement Technology and Intelligent Electronic Devices
• Accompanying website to include Solutions Manual for instructors

Protection of Modern Power Systems is an essential resource for students, researchers, and system engineers looking for a working knowledge of this critical subject.

Janaka Ekanayake, Cardiff University, UK
Professor Ekanayake is currently at the Institute of Energy at Cardiff University. As module leader on an MSc course, he teaches intelligent electronic devices, their applications and automation. He also teaches power electronic applications to power systems, flexible ac transmission systems and HVDC. Prior to this he was a Research Fellow at University of Manchester. He was promoted to Professor in Electrical and Electronic Engineering at the University of Peradeniya, Sri Lanka in 2003. Professor Ekanayake has published over 25 papers in refereed journals.

Jayasiri Karunanayake, Resource Management Association, Sri Lanka
Mr Karunanayake has worked in the electricity power industry for 40 years. He has been a protection engineer in Sri Lanka and abroad, where he has managed medium voltage distribution protection systems, analyzing system faults and maintaining all protection equipment in the generating stations and transmission systems. He has been a visiting lecturer in power system protection for undergraduate and post graduate courses at the University of Moratuwa, Sri Lanka. Mr Karunanayake has also served in committees, investigating several total system failures at the invitation of the Sri Lankan utility/regulatory authority. He is a member of IEEE, also the Institution of Engineers Sri Lanka.

Vladimir Terzija, University of Manchester, UK
Mr Terzija has worked in the field of power system protection for over 25 years, and in the area of WAMPAC for 15 years. He has published over 250 journal and conference papers and is chair of the Cigre WGB5.14 "Wide Area Protection and Control Technologies". Mr Terzija is a member of several IEEE Working Groups / Task Forces on Wide Area Monitoring, Protection and Control, and a member of the IEEE Protection Relaying Committee.

Contents

Preface xiii

About the Authors xv

List of Abbreviations xvii

About the Companion Website xix

1 Review of Principles of Protection 1

1.1 Introduction 1

1.2 Historical Development 1

1.3 Faults, Fault Currents, Voltages, and Protection 2

1.3.1 Types of Faults 2

1.3.2 Currents and Voltages under Fault Situations and Protection 2

1.4 Fault Current Contribution from Generators 5

1.5 Philosophy of Protection Relaying 5

1.5.1 Selectivity 5

1.5.2 Speed of Operation 5

1.5.3 Sensitivity 5

1.5.4 Reliability, Dependability, and Security 6

1.5.5 Primary and Backup Protection 6

1.5.6 Unit and Non-Unit Protection 6

1.6 Review Questions 6

1.7 Problems 6

2 Instrument Transformers 9

2.1 Introduction 9

2.2 Basic Principles of Operation 10

2.2.1 Shunt Mode 10

2.2.2 Series Mode 10

2.3 Current Transformers (CTS) 11

2.3.1 Steady-state Theory 11

2.3.2 Excitation Current 12

2.3.3 Excitation Characteristic 13

2.3.4 Terminal Marking and Polarity 13

2.3.5 CT Burden 14

2.3.6 CT Errors 14

2.3.7 Accuracy Classes 15

2.3.8 Accuracy Limit Factor 16

2.3.9 Rated Currents 16

2.4 Transient Response of CTs 17

2.4.1 Power System Fault Current 17

2.4.2 Flux Required to Transform the Primary Current 18

2.4.3 Transient Factor 19

2.4.4 Peak Transient Factor 20

2.4.5 Maximum Peak Transient Factor () 21

2.4.6 Transient Dimensioning Factor Ktd for Specific Time  21

2.4.7 Rated Equivalent Limiting Secondary Voltage (Eal) 22

2.4.8 Primary Time Constant (TP) with Multiple Infeeds 23

2.4.9 Over-dimensioning Factor (Kh) Due Remanence 23

2.4.10 Duty Cycle 23

2.4.11 Auto-reclosing 23

2.4.12 Errors 24

2.4.13 CT Classes for Transient Performance 25

2.5 Selection of a CT 26

2.5.1 Rated Primary Current 26

2.5.2 Rated Secondary Current 26

2.5.3 Class, Burden, and ALF of the CTs 27

2.6 Voltage Transformers 32

2.6.1 Inductive Voltage Transformers 32

2.6.2 Inductive Voltage Transformer Errors 33

2.6.3 Inductive Voltage Transformer Classes 33

2.6.4 Inductive Voltage Transformer Selection 34

2.6.5 Terminal Marking 35

2.6.6 Inductive Voltage Transformer Transient Behaviour 35

2.6.7 Voltage Transformer Connections 35

2.7 Capacitor Voltage Transformer 36

2.7.1 Capacitive Voltage Transformer Errors 37

2.7.2 Capacitive Voltage Transformer Classes 37

2.7.3 Transient Behaviour 38

2.8 Non-Conventional Current and Voltage Transformers 39

2.8.1 Introduction 39

2.8.2 Non-Conventional CTs 40

2.8.3 Optical Voltage Transformers 45

2.9 Review Questions 45

2.10 Problems 46

3 Review of Principles of Protection 49

3.1 Introduction 49

3.2 Excess Current Protection 49

3.2.1 Discrimination by Current 50

3.2.2 Discrimination by Time 51

3.2.3 Discrimination by Time and Current 52

3.2.4 Inverse Characteristics 52

3.2.5 Grading of Relays 54

3.2.6 Co-ordination with Fuses 55

3.2.7 Plug Setting and Plug Setting Multiplier 56

3.2.8 Time Multiplier Setting 56

3.2.9 Discrimination When There Is a Delta-star Transformer 56

3.2.10 Earth Fault Protection 61

3.2.11 Directional Relaying 61

3.3 Differential Protection 62

3.3.1 Transformer Differential Protection 63

3.3.2 Protection Against Inter Turn Faults and Earth Faults 65

3.3.3 Feeder Differential Protection 70

3.4 Distance Protection 73

3.4.1 General Principles 73

3.4.2 Zones 74

3.4.3 Characteristic Presentation 75

3.4.4 Distance Relay Inputs for Three-Phase Faults and Phase-to-Phase Faults 75

3.4.5 Relationship Between Relay Voltage and ZS / ZL Ratio 76

3.4.6 Distance Measurement 77

3.4.7 Distance Relay Tele-protection Schemes 77

3.5 Overload Protection 79

3.5.1 Overhead Lines 80

3.5.2 Transformers 80

3.5.3 Generators 81

3.6 Load Shedding 81

3.7 Over-Flux Protection 84

3.8 Review Questions 84

3.9 Problems 85

4 Protection of Distributed Generation 91

4.1 Introduction 91

4.2 Fault Current Contribution from Different Generators 92

4.2.1 Synchronous Generators 92

4.2.2 Single-fed Induction Generators 93

4.2.3 Doubly-fed Induction Generators 94

4.2.4 Full Power Converter Generators 95

4.3 Protection of Distributed Generation 96

4.3.1 Protection of Faults within a DG 96

4.3.2 Protection Requirements for DGs Connected to a Distribution Network 97

4.3.3 Distribution System Earth Fault Protection 99

4.3.4 Mains Failure Protection 100

4.4 Effect of DG on Distribution Network Protection 101

4.4.1 Blinding of Protection 101

4.4.2 False Tripping 105

4.4.3 Issues with Recloser Operations 108

4.4.4 Impact on Distance Protection 110

4.5 Review Questions 111

4.6 Problems 111

5 Protection of Wind Farms 115

5.1 Introduction 115

5.2 Wind Turbine Configurations 115

5.2.1 Fixed Speed Wind Turbines 115

5.2.2 Doubly Fed Induction Generator Wind Turbines 116

5.2.3 Fully Rated Wind Turbines 116

5.3 Wind Turbine Fault Protection 117

5.4 Protection of On-shore Wind Farms 121

5.4.1 Protection Associated with Grid Interface 121

5.4.2 Protection Associated with Collector Network 124

5.4.3 Lightning and Surge Protection for Wind Farms 128

5.5 Protection of Offshore Wind Farms 129

5.5.1 Protection of LCC-HVDC 131

5.5.2 Protection of VSC-HVDC 131

5.6 Review Questions 133

5.7 Problems 134

6 Protection of PV Plants 137

6.1 Introduction 137

6.2 Components of a Solar PV Plant 137

6.2.1 PV Cells, Modules, or Arrays 137

6.2.2 Power Conversion and Conditioning Equipment 141

6.2.3 Controller 143

6.3 Protection of Rooftop Solar PV Systems 143

6.4 Protection of Ground Mounted Solar PV Systems 145

6.5 Review Questions 151

6.6 Problems 151

7 Signal Acquisition and Processing for Intelligent Electronic Devices 153

7.1 Introduction 153

7.2 Signal Parameters for an Intelligent Electronic Device 153

7.2.1 Signals under Normal and Abnormal Conditions 153

7.2.2 Spectral Content of CT/VT Measurements 154

7.3 Nyquist Sampling Theorem and Aliasing 155

7.4 A to D Conversion 158

7.4.1 Sampling 158

7.4.2 Quantisation and Encoding 159

7.4.3 Issues with A to D 160

7.4.4 A to D Conversion Techniques: Successive Approximation Method 163

7.5 Discrete-Time Signal Analysis 164

7.5.1 Discrete Fourier Transform 165

7.6 Sine and Cosine Filter 168

7.7 Review Questions 172

7.8 Problems 172

8 Numerical Relays 175

8.1 Introduction 175

8.2 Components of a Numerical Relay 175

8.2.1 I/V Converter 176

8.2.2 Anti-aliasing Filter 176

8.2.3 Sample and Hold Circuit, Multiplexer, and A to D Converter (ADC) 178

8.2.4 Microprocessor 179

8.3 Numerical Overcurrent Relay 180

8.4 Numerical Distance Relay 180

8.5 Numerical Differential Protection 186

8.6 Review Questions 188

8.7 Problems 188

9 Substation Automation and IEC 61850 191

9.1 Introduction 191

9.2 Substation Automation 192

9.2.1 Input/Output Devices 192

9.2.2 Relaying and Controlling Equipment 192

9.2.3 Remote Terminal Units 193

9.2.4 Station Computer 193

9.2.5 Human-machine Interface 193

9.2.6 Supervisory Control and Data Acquisition System 194

9.3 Communication between Substation Equipment 194

9.3.1 Physical Media for Communication 194

9.3.2 Serial Communication 196

9.4 Connection of Substation Equipment 198

9.5 IEC 61850 200

9.5.1 The IEC 61850 Data Model 200

9.5.2 Time-critical Information Exchange 206

9.5.3 Sampled Values 209

9.5.4 SA Design 210

9.6 Review Questions 211

9.7 Problems 212

10 Wide Area Monitoring, Protection, and Control Fundamentals 215

10.1 System Needs for Wide Area Monitoring, Protection, and Control 215

10.2 Synchronised Measurement Technology 216

10.2.1 Definition of Synchrophasors 217

10.2.2 Synchrophasor Measurement Errors 218

10.2.3 Timing Sources 219

10.2.4 Phasor Measurement Unit 220

10.2.5 PMU Measurement Latency 221

10.2.6 Phasor Data Concentrators 222

10.2.7 Communication Infrastructure 223

10.2.8 Architecture of Synchrophasor Measurement Systems 224

10.2.9 Communication Networks for WAMPAC System 225

10.3 Wide Area Monitoring, Protection, and Control Applications 226

10.3.1 Post-disturbance Analysis and Model Validation 228

10.3.2 Characterisation of Load Centres 229

10.3.3 Monitoring of Parameters of Synchronous Generators 232

10.3.4 PMU-based State Estimation 233

10.3.5 PMU-based Monitoring of Inter-area Oscillations 239

10.3.6 PMU-based Coordinated Power Oscillations Damping 240

10.3.7 PMU-based Adaptive Underfrequency Load-shedding and Smart Frequency Control 242

10.3.8 Adaptive PMU Based Fault Location Method 245

10.3.9 Transmission Line Fault Location Based on Time Synchronised Samples 248

10.4 Practical WAMPAC Examples and Installations 252

10.4.1 Future Intelligent Transmission Network Substation (FITNESS) Project 253

10.4.2 Visualisation of Real Time System Dynamics Using Enhanced Monitoring (VISOR) Project 254

10.4.3 The Enhanced Frequency Control Capability (EFCC) Project 258

10.5 Review Questions 260

Index 265

The New copy of this book will include any supplemental materials advertised. Please check the title of the book to determine if it should include any access cards, study guides, lab manuals, CDs, etc.

The Used, Rental and eBook copies of this book are not guaranteed to include any supplemental materials. Typically, only the book itself is included. This is true even if the title states it includes any access cards, study guides, lab manuals, CDs, etc.